With the rapid development of computer technologies, computers are popularized, bringing users great convenience. In particular, portable computers make users be able to handle business on the go. To meet users' needs, the processing speeds of current computers increase day by day. Increasing the processing speeds of computers can enhance the performance of the computers. However, relatively more power will be consumed. It is not a big issue for desktop computers. Nevertheless, for portable computers, because it will cause the portable computer consume the power of batteries, the using time of the portable computer will be affected. Thereby, how to reduce the power consumption of portable computers becomes an important challenge. In addition, when supplying external power to the portable computers, how to increase the processing speeds of the portable computers to provide users with higher using performance also becomes a significant challenge.
Nowadays, in order to solve the problem described above, the vendors of portable computers make the operating frequency of the front side bus, which is between the central processing unit (CPU) and system chip, adjustable by users so that the portable computers can save power when supplied by batteries. Because the operating frequency of the front side bus is determined by the host clock signal, which is the fundamental clock signal of the front side bus, generated by the clock generator, thereby adjusting the operating frequency of the front side bus can be achieved by adjusting the frequency of the host clock signal.
Currently, the adjustment method is changing the operating frequency of the front side bus by means of the Basic Input/Output System (BIOS) at computer startup. Substantially, the configuration of the clock generator is changed to generate the host clock signal and the computer is rebooted. Thereby, after the computer is rebooted, the clock generator will generate the host clock signal according to the new configuration to adjust the operating frequency of the front side bus. According to the above description, it is known that each time when the operating frequency of the front side bus is adjusted, the steps of shutting down and rebooting the computer has to be carried out repeatedly, which is relatively inconvenient to users.
Thereby, nowadays, in order to solve the problem described above, the vendors of portable computers make the operating frequency of the front side bus adjustable by users when the computer is in operation. However, when the front side bus is in operation, if the operating frequency of the front side bus is adjusted substantially, that is, the host clock signal is adjusted substantially, the normal operation of the front side bus will be affected, which in turn will cause the computer crashed easily. Consequently, currently the operating frequency of the front side bus can be adjusted in small ranges each time. For example, it can be adjusted by 1 MHz each time. Thereby, if the user needs to adjust the operating frequency substantially, it can only be achieved by repeated small-ranged adjustments, which is very inconvenient. Furthermore, such small-ranged adjustments achieve the purpose of adjustment by changing the configuration via system management bus. The process of such kind of adjustments is quite complex; thereby the adjustment efficiency is low.
Accordingly, the present invention provides a switching circuit and method thereof for dynamically switching host clock signals to solve the problems described above. The switching circuit and method thereof can switch the host clock signals substantially when the computer is in normal operation. That is, the fundamental clock signal of the front side bus is changed to adjust substantially the operating frequency of the front side bus. Thereby, the users can adjust conveniently so that the power consumption of portable computers can be reduced, or the processing performance of portable computers can be enhanced.